Transcription
How's life everybody? I hope you're doing fine. In the previous video, we have talked about the direct Coombs test. Now let's talk about the indirect Coombs test, also known as indirect antiglobulin test or IAT.
Unlike the direct Coombs test where we were looking for antibodies on the surface of RBC's, here in the indirect Coombs test we are searching for antibodies floating in the serum, in the plasma, unbound to the red blood cells. So our goal is to detect antibodies in the plasma. The steps here are more than the steps of the direct Coombs test. We start with the patient's plasma, because we are looking for antibodies in the plasma. Then we add prepared RBC's of known antigenicity--red blood cells of antigens that we know. Unlike these antibodies, which we do not know, so when they go together they will form antigen-antibody complex on the surface of the red blood cell. Then we add the Coombs reagents, which are antibodies to human globulin. They will form red cell agglutination. This clumping is visual in the test tube. When clumping occurs, it's a positive test; when it doesn't occur, it's a negative test. So that's fine.
Why use indirect Coombs test? We use indirect Coombs test in the process of cross-matching before giving blood to a patient. So, antibody screening in pre-transfusion testing, that's number one. Number two is to screen pregnant women for antibodies that can cause hemolytic disease of the newborn. So, first to screen in pre-transfusion settings; second, to screen pregnant women for hemolytic disease of the newborn. That's the indirect Coombs test.
I'll see you in the next video. Please stay safe and study hard.